1. Field of the Invention
The present invention relates to an automatic greasing system and an abnormality detecting method therefor for a construction machine, such as a hydraulic excavating machine which is equipped with an earth working machine. The work machine is mounted on an upper swivel body of the excavating machine and comprises working members such as an arm member and an earth working tool, such as a bucket, which are articulation-connected to carry out earth moving work such as excavation by swinging these working members with hydraulic cylinders which are pin-connected between the arm member and the earth working tool.
2. Description of the Related Art
In general, those parts of construction machines, such as hydraulic excavating machines, for which greasing is required, that is, those pin-connected parts of earth working machines, such as an arm member and a bucket, are directly greased by an operator with a grease gun through the end faces of the pins or the bushes and bosses into which the pins are inserted. However, some construction machines are provided with a centralized greasing port for greasing several pin connections by supplying grease to these pin-connected parts. In the case of conventional greasing with the grease gun, the operator has to move about in order to reach the greased parts of the machine, since the greased parts are in dispersed locations. Therefore, it is troublesome for the operator to finish such greasing service. Since greasing is directly performed by the operator with the grease gun in this prior art method, the operator's clothing may become soiled with grease. In addition, as earth and sand are detrimental to machines, construction machines which handle earth and sand should be periodically greased at a greasing interval specified by the manufacturer. If the specified greasing interval is ignored, possible results include seizure of pins and bushes, production of loud sound or noisy rattling sound due to an increase of clearance between pins and bushes resulting from wear, and deterioration of durability due to development of wear caused by mud and sand which have entered into the pin-connected parts. Recently, an automatic greasing system for construction machines (Japanese Patent Application Laid-open No. 190837-1989), as shown in FIG. 12, has also been invented. In FIG. 12, a grease pump 38, connected to a pressure-accumulated grease tank 44, is provided on an upper swivel body 5 of a hydraulic excavating machine 1. A discharging port of the grease pump 38 is connected to a master distribution valve 52, and slave distribution valves 53 and 54 are connected in series to the downstream side of the master distribution valve 52. Each of the diverting ports of the master distribution valve 52 and the slave distributing valves 53 and 54 is connected by a greasing pipe to a respective one of the swivel bearing 3 of the swivel body 4, and the pin-connected parts 12-14, 18, 19, 21, 23, 25, 26, 30, and 31 for the work machine. On the other hand, a controller 20 is provided in an electric circuit which connects a battery 42 and a grease pump drive motor 43, which are located on the hydraulic excavating machine 1. The grease pump drive motor 43 can be operated by the controller 20 when an engine 50 has been operated for a predetermined cumulative time. In addition, when greasing from the master distribution valve 52 and slave distribution valves 53 and 54 to respective pin-connected parts 12-14, 18, 19, 21, 23, 25, 26, 30, and 31 is finished, the grease pump drive motor 43 can be stopped. After lapse of the above-described predetermined cumulative time, the operation of the grease pump 38 can be repeated.
The following describes the operation of the related art shown in FIG. 12. A key switch 48 is turned on and a manual switch 51 is set to the automatic greasing position in advance. When the engine 50 has been operated for the predetermined cumulative time according to a time function of the controller 20, the grease pump drive motor 43 starts operation by actuating the grease pump 38, and therefore grease 45 from the pressure-accumulated grease tank 44 is supplied by the grease pump 38 to the slave distribution valves 53 and 54 through the master distribution valve 52. At the same time, the grease 45 is distributed from the respective diverting ports of the master distribution valve 52 and the slave distribution valves 53 and 54 to the swivel bearing of the swivel body 4 and to the greasing ports of the pin-connected parts 12-14, 18, 19, 21, 23, 25, 26, 30, and 31 for the work machine 8. Therefore, all of the swivel bearing 3 and the pin-connected parts 12-14, 18, 19, 21, 23, 25, 26, 30, and 31 are automatically lubricated. The above greasing operation is finished when a limit switch 40, provided in the master distribution valve 52, operates to output its switch signal to the controller 20. The grease pump drive motor 43 is stopped according to a command of the controller 20, thereby simultaneously stopping the grease pump 38. Thus, while the grease pump 38 is in a stopped state, the engine 50 is started to make the hydraulic excavating machine 1 carry out the work. In this case, when the cumulative time of operation of the engine 50, as accumulated by a service meter 49 from the restarting of the engine 50, reaches the predetermined cumulative time, the operation process of the grease pump 38 as described above is repeated. If the hydraulic excavating machine 1 is not used for a long period of time, the greasing operation can be carried out as required by operating the manual switch 51. However, the automatic greasing system for the hydraulic excavating machine according to the related art is adapted to operate the grease pump drive motor 43 according to the timer function of the controller 20 to actuate the grease pump 38 when the engine 50 is operated for the predetermined cumulative time and to supply grease from the pressure-accumulated grease tank 44 through the grease pump 38 to the articulated connection parts 12-14, 18, 19, 21, 23, 25, 26, 30, and 31 of the work machine 8 through the master distribution valve 52 and the slave distribution valves 53 and 54. Accordingly, the time when the operator is away from the operator's seat and the engine is idling only for warming up, and the time when the engine is driven only for traveling, even though only the engine 50 is driven, are included in the cumulative operating time of the engine 50. Therefore, the grease pump drive motor 43 is operated according to the timer function of the controller 20 without regard to the operating time of the articulation-connected parts 12-14, 18, 19, 21, 23, 25, 26, 30, and 31 and of the swivel bearing 3 of the work machine 8. Thus, the grease from the pressure-accumulated grease tank 44 may be unnecessarily distributed to the articulation-connected parts 12-14, 18, 19, 21, 23, 25, 26, 30, and 31 and the swivel bearing 3 of the work machine 8 by the grease pump 38 through the master distribution valve 52 and the slave distribution valves 53 and 54. For this reason, the above-described automatic greasing system has been defective in an uneconomical use of grease, a contamination of the hydraulic excavating machine 1 and its ambiance due to overflows of excessive grease from the greased parts, and the like. Moreover, the greasing pipes for greasing the articulation-connected parts 23, 25, 26, and 30 of the work machine 8 can be damaged by earth and stones. In addition, when the above-described automatic greasing system is provided, an abnormality of this greasing system is displayed on a warning element of the monitor panel in the operator cabin. In this case, a signal is generated from the greasing system to the warning element of the monitor panel only when an abnormality occurs in the greasing system. In other words, according to the idea of the related art, when the system is normal, a low level (=0 V), at which no signal is generated to the warning element, is maintained between the controller 20 of the greasing system and the warning element. Only when an abnormality occurs in the system is the circuit therebetween changed over to a high level (for example, 24 V), and the abnormality warning produced. However, if it is adapted to generate a high level warning signal only when the system is abnormal as described above, the operator may continue the operation without being aware of an abnormality, and the work machine can be damaged due to seizure of the pins of the work machine when the warning signal is not generated to the warning element despite the fact that the system may not be capable of supplying grease to the greased parts, for example, when a fuse at the system side of the controller 20 is blown.
An object of the present invention made to eliminate the defects of the related art is to provide an automatic greasing system for construction machines capable of automatically supplying grease to the greased parts, and to provide an abnormality detecting method therefor capable of also detecting an abnormality of the controller 20 of the automatic greasing system. Moreover the present invention also provides an automatic greasing system for construction machines which is capable of eliminating such defects as an uneconomical use of grease, a contamination of the hydraulic excavating machine 1 and its ambiance due to overflow of excessive grease from the greased parts, and the like, since the articulation-connected parts 12-14, 18, 19, 21, 23, 25, 26, 30, and 31 and the swivel bearing 3 of the work machine 8 are greased despite the fact that the total operating time of the articulation-connected parts 12-14, 18, 19, 21, 23, 25, 26, 30, and 31 and the swivel bearing 3 of the work machine 8 has not reached the predetermined value.